Momster' and Sons
by Angela Evil
Summary: An AU where Gaster is female (I wanted to write a mother&son dynamic) and actually a good parent. It covers a few major events from Sans POV and introduces some background. Goes along with a comic I'm drawing. I'm posting this because I feel like it, hope you enjoy it though.
**FYI: Each line break is a time skip. The first scene is when the skelebro's are 12-ish, and they are twins in this go round with Sans being the older twin.**

* * *

Sans drummed his digits against the desk top, seething at his project. Nothing was working. Every formula a failure. Every mechanical adjustment cracking under pressure. Why wasn't the quantum tunnel stabilizing?

He let his skull smack onto the wood surface with a groan. This was so much easier on TV. Or even when Gaster was working. Now that monster could work magic! Papyrus' cheery Nyeh-ing cut through his brooding efficiency. At least his brother was having better luck with his assignment.

Sans peeled his skull off the desk and turned his lazy grin towards the orange-clad skeleton behind him. Paps was running through some simulations of non-lethal traps while twisting around a color cube puzzle Gaster had given him for the brothers' birthday. Just seeing the light dancing in Paps eye sockets was enough.

He returned his gaze to the desk, determined to find a solution.

Like that, hunched over his work, calculating and recalculating, the day passed quickly. At one point, when Papyrus was waiting for several pages of data to print off, the taller brother leaned in to see what Sans was slaving over. They were allowed to indirectly help according to Gaster's challenge rules so the blue skeleton vented to his orange counterpart. Paps made an inciteful comment about the logical mechanics of the device, as opposed to the scientific which Sans had been racking his skull with all day, and everything just clicked.

It did work.

Sans was just overthinking things.

The shorter skeleton shot out of his chair, wrapped his arms around Paps waist, and hoisted his brother into the air despite their growing disparity in height. "you are the best bro a guy could have, paps!"

"Nyeh He He! I Am The Great Papyrus After All! It Only Makes Sense That I Would Be The Best!"

" **You boys look like you're having a good time.** " Sans set Papyrus down and turned toward the voice. Gaster was leaning against the door frame holding her '#1 Momster' mug, a proud smile gracing her predominantly smooth face.

"Mother!" Papyrus ran over and hugged Gaster, his head only reaching her hip. Sans also approached though at a more leisurely pace and joined in on the hug, humming happily.

" **So, how's the homework coming along?** " She grinned down at them and strode into the room with a baby bones attached to each leg.

The Skeleton Brothers' room was connected to Gaster's private quarters on the Lab's upper floor just off the main living space. Two twin beds were scooted up next to each other along the back wall. The messier of the two was Sans's obviously. Each had a bookshelf, a beside table, and a desk with their belongings and work piled on. In everything else Sans was a slob, but his workstation was pristine and meticulously organized. Papyrus' was overflowing with sticky notes and prototypes. An organized chaos. Between the door and the desks was a large section of tiled floor and a clean metal table. The brothers used it for experiments in chemistry, physics, and even biology on the rare occasion they had something to work with.

There was also a mini lab set up in the living room which could be seen if one peeked around the doorway to the right. Gaster's rooms were at the end of the hall, the entrance not five feet from the brothers' door and to the left.

Sans' mind flipped through his explorations of their living quarters while he watched his mother review Papyrus' work. The taller skeleton child had let go and proudly explained everything to Gaster in detail. Sans remained attached to her leg however, studying the way her expression changed with each word from his younger twin. There were some days Sans noticed an expression he couldn't place when Gaster didn't think anyone was looking. He didn't know what to make of it. He sometimes didn't know what to make of her. It only then occurred to him, that neither he, nor Papyrus had ever left the living quarters. Ever.

The space was essentially a house on top of a laboratory their mother rarely left. They certainly didn't. Far too dangerous for the young skeletons. Besides Gaster was the most qualified of teachers in the Underground anyway. But it still nagged at Sans, like she was trying to keep them a secret. He wanted to do more. See more. To explore what was out there and not just sit here learning about the world from books.

He didn't realize he'd been caught staring until Gaster placed her hand on his skull with a sad smile. Sans knew he was being groomed for something and Gaster knew he knew. That look in her eye sockets told him so.

" **Do you boys want to see where Mommy works?** "

"yeah!"

"We Get To See Your Lab!"

* * *

If Sans was honest, it was all a bit much. He was excited and scared and then excited again. Little beads of sweat dappled his skull while he clutched Gaster's hand for dear life. He had never been in an elevator before. Heak he didn't even know that their front door was an elevator!

Papyrus couldn't stop bouncing. Sparkles of magic lighting up in the air around his head. Sans felt a little dizzy from it actually.

Gaster chuckled at her son's enthusiasm while rubbing her thumb over Sans' hand soothingly. All the while the shorter baby bones wondered at how he could be related to Papyrus in the embarrassed older brother way that was neither derogatory nor meaningful.

When the doors opened Sans just gaped at the size of everything. There were tables hold humming, buzzing machines. Wonderment sparking in his ribs as he began to recognize different instruments and devices. The fact that he knew what some of the equipment was and how it worked thrilled him in a way he hadn't expected.

Workers, different monsters he'd seen pictures of with his mother in different newspapers and magazines she'd given them, milled about in the lab. The low buzz of conversations and the occasional louder voice through the opened space was more than a little overwhelming for someone as used to the quiet as him.

"Ah! Doctor Gaster!" A large, burly reptilian monster gently pushed through a crowd of workers. His golden scales glinted from beneath his lab coat. When he came to a rest his legs bunched up, clearly not built for properly standing upright, his tail acting like a weight to keep him bipedal. The lab worker seemed to notice them for the first time.

Sans had taken a step behind Gaster's leg as had Papyrus. Neither of the skeletons apparently retaining their bravado in spite of their immense curiosity.

" **Good afternoon, Alder. And how is Alphys doing? Adjusting to a new work environment must be hard on her.** "

"A-ah, yes Doctor. She's been such a wonderful assistant. Thank you for letting her intern here." He looked to the side, a proud shine in his eyes. "To think my daughter working under her idol. Really she's not be so fluent in her speaking in months. It's nice to see her happy."

" **Haha, yes. But she did deserve the position, Alder. Make sure you remind her of that.** "

"And who are these adorable little hatchlings?" The dragon-like monster leaned down to better examine Sans.

" **These are my sons, Papyrus and Sans.** "

"An upper-caser and a lower-caser? In one clutch. Why I'd never think they'd get along but look at them! So fascinating." Alder paused for a moment, his eyes traveling to Gaster's as he straightened up. He seemed nervous and apologetic, glancing around the lab with worry. His deep voice dropped into a whisper, "I-I don't mean to question your judgement Doctor but… it's not safe. There are those here more loyal to Asgore than to you."

" **I know.** " Sans flinched at the coldness in Gaster's tone, mournful and trepidatious. It sobered him. " **Children grow and need to experience the world. I won't be around to protect them forever, no matter how much I might wish to.** "

Alder hesitated a moment before nodding. "I'll do my best to aide you."

" **Thank you, Alder.** "

"It's what friends do, Gaster. No thanks necessary."

* * *

Sans slouched into the den's armchair, brooding. Gaster's birthday was just around the corner and while all years prior Papyrus and he made homemade gifts, not that they could do anything else really, he finally had some way to buy something. He wanted it to be sentimental, comical, and memorable because that's what their mother had done for them.

He shrugged deeper into Gaster's oversized blue coat, feeling the wooly fur trim shift against his skull. Both he and Papyrus had gotten an extra present for their thirteenth birthday as a recognition of all their hard work over the past year and a welcome into the growing responsibilities. He picked the hoodie because it was comfortable, and because it smelled like Gaster. It only made sense that the blue fabric could calm and comfort him, it used to belong to his mother, and she'd worn it whenever she went out when they were still really little.

Papyrus chose a scarf. Probably because it looked like a cape when considering it was made for a skeleton of Gaster's height. Sans didn't doubt Papyrus would get taller though. Paps was always the bigger of them. More durable and energetic. Though Sans supposed he was less hyper for a reason other than general size.

"S-S-San-ns?"

"in here alph!" He recognized the high pitched stutter of Alder's daughter. Her much smaller figure waddled into the den with a nervous smile. The poor young dragon monster looked like, and in some cases was, a walking panic attack. "what you been up to?"

"T-trying t-to surp-pr-prise d-doctor Ga-ga…" she cleared her throat and her brow dipped in frustration, "Gaster."

"it's actin' up again?"

She clearly didn't trust her voice, opting to nod an affirmative. Sans could relate, if only partially, to her difficulty. Dragon monsters usually spoke using pulses from their souls and growling clicks. Forcing her mouth to move in a way very foreign to her nature was difficult. It certainly didn't help that she had a quite, abnormally shy, disposition.

Sans had found it difficult to move out of windings. Both he and Papyrus hadn't even noticed they weren't being understood until Alder had gently informed them. It was embarrassing, but fortunately Alder had picked up enough of Gaster's coded language to understand it. Just anyone else in the lab would have no clue what they were saying. He sometimes forgot words, only coming up with the wingding for it. Paps was better at adapting out but both brothers had the habit of slipping back when they were frustrated or distressed.

It certainly helped make a closer association with the only other monster his age, aside from Papyrus, who was working in the Lab.

"G-got a-any ideas-s-s?"

Sans shrugged, much to Alphys' disappointment. "'at's what i've been tryin' to wrap my skull around the past hour, alph. sorry i'm not much help."

Papyrus shot past, halting by the archway separating the den from the hall. "Brother!" He shouted in wingdings, a slight edge of panic in his voice. Alphys jumped at the taller brothers sudden appearance.

"What's up, pap?" Sans leaned forward in the seat, also speaking in wingdings. It was just easier.

"I Can't Find My Left Arm!"

"what?" Sans stood and walked briskly over to his brother's side. Sure enough Papyrus was missing his left arm just beneath his elbow. The taller skeleton was beginning to panic. Sans could hear Alphys suck in a breath as she waddled up beside him. For her sake he switched back to something understandable. "how did you manage to lose your arm, paps? what were you doing!?"

"I-I Um… Many Have Been Experimenting With The Void As A Transportation Method For A Trap…" Papyrus looked down in chagrin.

Sans slapped a bony hand to his skull and moaned. "how many times have i told you not to mess with my VTR device when i'm not around? you could have seriously hurt yourself, pap!"

"U-um, w-what's a V-VTR d-device?"

"jus' somethin' i've been workin' on." Sans had almost spilt his work to Alphys who would have told Gaster, who would in turn have been furious with him for experimenting with something so dangerous. Still Sans thought he had the prototype locked out of Papyrus' reach but apparently not! "c'mon, pap, let's go get your arm back."

"... Sorry, Brother."

"look. i'm just glad you aren't hurt, bud, but you gotta think more about the consequences of your actions."

"Okay."

* * *

" **Alright, Sans. Let's see what you can do.** "

Sans took a deep breath and braced himself, magic crackling in his bones. The simulation chamber hummed as it started up. All he had to do was hit the target and avoid the paintballs, easy enough. He'd done this before, ever since he was twelve, though Gaster was loath to send him and Papyrus through combat training of any kind. She recognized it was necessary once they started working at the Lab.

He'd been perfecting his gravity magic, discovering he'd inherited Gaster's karmic poison ability in the process. Gaster admitted Sans was strong, exceptional with magic, but his stamina was… pathetic. She hadn't used that word but Sans knew his was abysmally short. Papyrus on the other hand had slightly less power, more finesse, and practically boundless stamina. If Sans was honest he'd admit to being a little jealous.

But he had a power his brother didn't. He could read souls like an open book, even without being in a confrontation. On the few times he encountered a member of the royal guard, he could sum them up in seconds and react accordingly. Sans could read people and predict them. For some reason, he felt stronger when facing down someone with a higher LV. Maybe that was his karmic poison power, maybe it wasn't. Who knows really. Gaster didn't seem to.

Sans didn't have much time to dwell on things as the first volley came at him, splattering color over the ground where he had just been standing. He summoned a few bones, striking targets that deactivated the paint ball turrets.

He cleared the trail in a record two 'turns' much to Gaster's delight.

Sans walked out of the chamber and passed Papyrus. When they were fourteen both brothers had a growth spurt but Papyrus was now easily a head and a half taller. "Wish Me Luck Brother!"

"heh. you don' need it, paps. you're already the greatest."

Sans moved into the control room where Gaster was setting up the next trial. She had started wearing a turtle-neck sweater under her tailored suit coat like she had done until they were five. He wondered why. She didn't seem very comfortable in it. Gaster had been growing increasingly more distant, that look he'd notice as a baby bones becoming more commonplace. He was worried.

"ya 'lright, mom?"

" **Yes, just,** " Gaster took a deep sighing breath and looked at him. Her normally glowing pupils were dim with sorrow, " **you two are growing up so fast. I almost don't want you to.** " A slight smile played at her face while she returned to the machinery.

Sans gave a nervous chuckle. "kids grow, ma. we don't stay baby bones forever."

" **Yes. Yes, I know. I've gotten you two a place in Snowdin. I think Papyrus will like it there.** "

"h-hu? a place? w-what are you talking about?" Sans moved closer and he could make out the beginnings of tears in Gaster's eye sockets.

She turned to smile warmly at him. The smile didn't reach her her eyes. " **You boys will be seventeen in a few weeks. I couldn't be prouder of my little men.** "

"gaster," rarely, if ever, did Sans actually use her name. Only when things were really bad or he needed her to be open. He could only count three times in his life, including this one. "what happened?"

She looked down at the controls and started up Papyrus' combat simulation before turning to fully face Sans. " **You cannot tell Papyrus.** "

"alright."

Gaster took a deep breath and leveled her gaze to Sans.

" **I'm dieing.** "

* * *

Sans clutched his skull. He'd stormed off after getting into an argument with Gaster about telling Papyrus, about staying in Hotland and continuing to work at the Lab. She refused on all counts. He said some things he shouldn't have. Now here he was, sobbing on his bed in the dark, the realization that he and Papyrus were the ones killing her stabbing through his mind.

His gaze drifted over to the VTR. If Gaster used it then maybe she could eek out another decade or so. But that wouldn't be living, trapped in the void like that. He had based the design of off blueprints Gaster had drawn up, so maybe she had been considering something similar. If that's the case then she'd have dismissed it a long time ago.

He shoved himself off the his bed and began pacing. He had to do something. Anything! Gaster couldn't die, not yet. He wasn't ready for this- whoever could be?- and Paps certainly wouldn't be either.

Unbidden, Sans nihilistic predilections slumped into his shoulder blades. Gaster was going to die and there was nothing he could do about it. It was the monster life cycle. What he'd said… oh, gods. All those awful, untrue things shouldn't be the last words he ever shares with his mother. He needs to apologize, to be with her for the last few days she might have.

Sans grabbed his jacket and jumped down into the lab space. His little hoping trick really came in handy for getting places quickly at least.

It took him less than a second to notice something was up. No one was working today, not even Alphys. The lab was completely empty. "gaster?" The echo of his voice settled disquietly in his ribs. Did she send everyone off so they didn't see her fall down? Was it really happening this soon?

Panic forced Sans feet into rapid pace, calling Gaster's name again and again. A light from the open security door caught his attention. The tape that should be recording the events at the Lab and Core were unplugged. Sans' focus was on the screen however. Gaster was standing by a turbine to the Core, looking into her creation while Asgore, looking uncomfortable, wary even hung back from the edge a little ways.

"I am here, Gaster," the ancient king rumbled, "may I ask why?"

Gaster lifted her head and turned just enough to look him in the eye. " **I wanted to say good-bye.** "

Asgore's face softened, voice gentle. "I see. It is finally time then?"

Gaster nodded.

"Don't worry about your sons; I'll take good care of them."

" **No… you won't.** "

Sans swallowed. Both monsters on screen tensed, Asgore's voice coming out as a low growl. "What do you mean by that?"

" **I mean that you will** _**not**_ **turn my sons into weapons. I mean that they will not participate in your foolish war of vengeance.** " Gaster's voice was growing sterner just as it was growing louder. " **I mean** _ **that Toriel was right to leave you**_ **because you cannot see past your own sorrows at the suffering you are causing to others!** "

Asgore flinched at the mention of his wife. A chastised look in his eyes and the wrinkle of anger in his snout.

" **Consider this my resignation, Dreamurr.** " Sans gasped at the magic his mother let loose. The two boss monsters where fighting. It looks like Gaster would have an easy win, especially after she summoned her entropy cannon- which Sans had affectionately dubbed the Gaster Blaster- only now he was seeing the rest of it, not just the skull. " **Here is that weapon to use against humanity you wanted, by the way.** " Gaster was pushed back by Asgore's fire magic to the edge of the core.

"no! mom look out!"

Gaster didn't hear him of course. His grip on the counter the only thing keeping him from jumping to her side. He might be good at dodging but this exchange between the two boss monsters was a small war zone. With his measly one hp, he'd be dead the second he stepped foot in the Core.

They had stopped fighting, Gaster clutching her side in agony while fractures spiderwebbed out from her already existing cracks. She was breathing heavily, letting out a sad laugh. " **It's fine to hate me, Asgore… Those experiments I was running on DT… I'm afraid Alphys will repeat them without the benefit of learning from my mistakes. DT cannot be made into medicine like I'd hoped, there are too many side effects. Even now I still feel it burning in my marrow.** " Gaster knet her face contorting in pain. " **I've done everything I can. I've been lucky DT worked at all… But that's all fine I suppose. I don't hate you, Asgore. Even after all this, you are still my friend… I'm done REFUSING… I'll be forgotten by everyone… not a trace left of me anywhere…** " A portion of Gaster's skull had started melting, her hands were already fusing, and her spine too if her hunched posture was anything to go on. " **I'll take it with me… your hatred. No more war.** " She laughed mirthlessly, teetering dangerously close to the edge now.

Sans tried to jump but it was like running into a wall full speed. He bounced off the space where Gaster and Asgore were, landing heavily on his tailbone still in the security office. "ow."

" **Peace… finally… Sans, tell Papyrus 'I love you'. I hope you can forgive me for not giving you a chance but… I've been ready for this… good-bye, my** _ **sans**_ **ational little funny bone.** "

Sans was left to watch in ineffectual horror as Gaster lost her balance and tumbled headlong into the Core. Dust before she hit the bottom. His ribs clenched. Asgore seemed confused, looking around the Core as if he wasn't sure why he was there. The dark aura that had surrounded the monarch before vanished entirely, leaving a melancholic deepness in the monster. It was a pulse of magic, starting there and rippling out throughout the entire underground. It would be on him any second now.

Then there was nothing.

Dark.

Darker.

Yet Darker…

* * *

Sans shot off his bed, only to stumble out onto the floor with a loud thwump. Frisk peeked their little head around the door frame with a slight worry in their bunched up little face. "heh. i'm okay kiddo; a little rattled is all."

They nod, still giving him a weird look and shuffle off into the house.

The skeleton sat up, untangling himself from the sheets letting his brow crease. What had gotten him so riled, he normally remembered his nightmares… He let out a low sigh. "oh well, must not have been important if even i can't recall it." Saying that had left a stinging feeling in his soul and an ache in his rib cage that he couldn't place.

Anyway, new sunshine to live, new job to slack off at, new books to read. So much new going on, might as well get started now that he's up.

* * *

 **Great... now I'm sad...**


End file.
